Groundwater Monitoring

Submitted by admin on 11-03-2011

WPI currently provides groundwater monitoring services at approximately 200 sites throughout California and Nevada. We have the personnel, equipment and experience to handle any groundwater monitoring assignment.

Every groundwater monitoring crew is supported by an administrative services staff member and a professional geologist or engineer. These employees are always available to the crew for unanticipated field situations.

Safety is always our top priority. Our groundwater sampling crews receive extensive training in the use of personal protection equipment, traffic control procedures, construction barricading and site control. In addition, every crew member receives 40 hours of initial HAZWOPER training, annual 8-hour refresher courses and holds a current American Petroleum Institute Safety Key.

An overview of our groundwater monitoring services is provided below.

Well Inspections: All wells to be sampled are located and inspected, and a Well Inspection/Purge Log is prepared for each. Any unusual occurrences (e.g., subsidence of the concrete cap) are noted. The well boxes are inspected to ensure that all bolts are present and the box itself is in good condition.

Each well box is then opened and the well head is inspected. Any water or trash that has accumulated in the well box is removed. Any missing locks or damaged caps/wellheads are noted on the field log for that well.

Well Gauging: After the inspections are completed, the depth to water in each well relative to the survey mark on the casing is gauged with an electronic water level indicator to within 1/100th of a foot. The depth to water is measured and recorded twice for every well to ensure accuracy. The depth to water and the existence and thickness of any immiscible liquid is recorded on the Well Inspection/Purge Log. After each measurement, the water level indicator is decontaminated by washing the indicator and tape in a solution of Alconox followed by triple rinsing in distilled water.

After the water level measurements are completed, each well is sounded, and its depth is recorded on the Well Inspection/Purge Log. After each measurement, the sounding tape is also decontaminated as described above.

Well Purging: The water level measurements, total well depth, and borehole or well casing diameter (as required by the local oversight agency) are used to calculate the pre-purge bore-hole\well casing water volume. Once this value is known, three bore-hole\well casing volumes are calculated, along with the depth to water at 80% of the bore-hole volume. These calculations are recorded on the Well Inspection/Purge Log.

The time that purging starts is recorded on the Well Inspection/Purge Log. As purging proceeds, water quality parameters (i.e., pH, temperature, conductivity, and turbidity) are measured periodically. These measurements and the volume of water removed are recorded on the Well Inspection/Purge Log. Care is taken to not purge a well to the point that it is completely de-watered.

When the water quality parameters have stabilized to within 10% of their respective previous measurements, and a minimum of one and one-half bore-hole volumes have been removed, purging of the well is considered completed. If the water quality parameters have not stabilized, purging is continued until three bore-hole volumes have been removed.

In either case, after purging is completed, the well is sampled when it has recovered to 80% of its pre-purge level. The time that 80% recovery is attained and the time the groundwater sample is collected are recorded on the Well Inspection/Purge Log.

Decontamination Procedures: Persons conducting purging and sampling wear appropriate personal protection equipment (PPE) during all operations. After purging operations are completed, the sampler dons new nitrile gloves before handling the sample containers. Gloves are changed between each sampling location.

Equipment that may be used for well purging at more than one location (e.g., portable pump and tubing) are decontaminated between each use by washing the exterior and interior in a non-phosphate detergent, then double-rinsing in distilled water. An equipment blank sample is collected following decontamination to confirm that cleaning procedures were adequate.

Sample Collection and Handling: Where dedicated pumps are installed, groundwater samples are collected directly from the pump discharge. Groundwater samples from monitoring wells without dedicated pumps are usually collected with disposable bailers. All samples are collected into clean laboratory supplied containers that are appropriate for the required analyses.

As each sample container is filled, it is labeled, sealed in a plastic bag, recorded on the chain-of-custody document, and placed in cold storage for delivery to the analytical laboratory. Samples are delivered to the testing laboratory following the last day of sample collection. Samples that are held overnight are stored in a secure location and maintained in a chilled condition.

Equipment Calibration: Water quality instruments are calibrated at the start of each day they are used during the sampling event. At the end of each day of use, the calibration drift is measured by placing the instrument in the appropriate calibration solution and recording the variance (if any). The calibration logs and results obtained by the calibration drift checks are included in Groundwater Monitoring Reports upon request.

Well Maintenance and Repairs: Minor repairs and replacement of screws, well caps, locks, and gaskets are performed at the conclusion of each groundwater monitoring site visit. There is no additional cost for labor, but materials are charged at cost plus 10%. If more extensive repairs are required, they will be noted on the Well Inspection/Purge Log, and a change order for the repair will be requested.